This invention relates to video observation systems, and more particularly to systems for recording scenes or objects for subsequent viewing by an observer, especially (although not necessarily) by an observer who is at a substantial distance from the scenes or objects. If such substantial distances are involved, then the systems of this invention facilitate the use of relatively low-cost transmission media between the original scenes or objects and the observer.
Although this invention has many other possible uses, the invention will be fully understood from an explanation of its use in identifying moving railroad freight cars, especially (although not necessarily) at locations remote from the observer required to make the identification.
Raymond et al. U.S. Pat. No. 4,264,927 (which is hereby incorporated by reference herein) shows a freight car identification system in which a remote track-side television-type camera is connected via a video signal transmission line to a centrally located videotape recorder. The system is automatically activated when a train approaches the camera and, while activated, videotapes a continuous side view of the train as it passes. As soon as the train has passed, the system shuts itself off until the next train approaches. At any convenient time, the operator of the system ("the observer") removes the recorded videotape from the recorder and plays it back on a playback machine in order to identify the freight cars in the train from the letters and numbers painted on the sides of the cars.
The system shown in the '927 patent works well and has achieved wide market acceptance. In some situations, however, it is desired to locate the camera at a considerable distance from the observer. In those instances it is usually quite costly--sometimes prohibitively costly--to provide the high-grade video communications link required between the camera and the videotape recorder. For example, railroads would frequently like to locate the camera many miles--sometimes 100 or more miles--from the observer. This may reduce the number of observation points a railroad needs by allowing greater centralization of the observation function. It may also reduce the number of employees required as observers. Heretofore, however, the high cost of long, video-grade communications links has been a major disadvantage of such otherwise desirable system configurations.
Even if the distances involved are relatively small (so that providing high-grade video communications links is not a problem) or if high-grade video communications links are available, videotape-based systems may have some disadvantages. For example, videotape systems have many mechanical parts which have relatively high maintenance requirements. The videotapes themselves are subject to wear and degradation. Videotape systems cannot operate unattended for extended periods of time because an operator is frequently required to change tapes. Tape speed is not dependent on train speed so that considerable amounts of tape are essentially wasted when recording slow-moving trains. Videotape is a linear recording medium, so that it is relatively difficult to view images out of order or at random. It is also not possible to simultaneously record and play back the same tape.
In view of the foregoing, it is an object of this invention to provide improved video observation systems.
It is another object of this invention to provide remote video observation systems which do not require high-grade communications links between the remote camera and the central observer.
It is still another object of the invention to provide improved remote freight car identification systems.